This invention generally relates to fasteners. More particularly, the invention relates to an apparatus and method for manufacturing masonry fasteners of the type used to secure structural elements and materials to masonry by forcibly driving the fastener into a hole, pre-drilled within the masonry.
In many instances there is a need to fasten a fixture or structural member to masonry, such as a concrete floor. Various masonry fastening systems are used in the industry including: nails driven directly into the masonry; multiple component expandable anchors used with pre-drilled holes in the masonry; and one piece masonry fasteners driven into a pre-drilled hole in the masonry. An example of the latter type of masonry fastener is described in copending U.S. patent application Ser. No. 918,663, filed Jul. 22, 1992, entitled MASONRY FASTENER, which is commonly assigned to the assignee of the present application.
This invention details an apparatus and method for manufacturing one-piece masonry fasteners which are intended to be driven into holes pre-drilled into the masonry. Masonry fasteners manufactured according to the present invention are constructed from constant diameter wire stock and include a body composed of a straight, constant diameter shank and a helical portion which generally defines a cylinder having a diameter greater than that of the pre-drilled hole with which it is intended to be used. The helical portion or helix of the fastener causes the fastener to rotate as it is driven into the pre-drilled hole. During this rotation, the outermost surface of the helix scores a helical groove into the masonry which defines the wall of the pre-drilled hole. These fasteners exhibit a high retentive force through a combination of features including: the frictional engagement of the fastener with the wall defining the pre-drilled hole; the deformation of the hole wall which creates conformity of the wall with the shape of the fastener; the increased surface contact between the wall and the fastener; the rotational turning of the fastener induced by the helix during attempted removal of the fastener from the hole; and the spring-like force exerted by the fastener on the hole wall as a result of the helix being deflected as the fastener is driven into the hole.
It is therefore an object of this invention to provide both an apparatus and a method for manufacturing a masonry fastener of the above described variety.
The apparatus and method of this invention are capable of manufacturing a masonry fastener having a body which includes a substantially cylindrical shank that terminates in a helix. The apparatus includes a pair of opposing tools or dies, each of which cooperate to define surfaces that clamp a wire stock workpiece between the dies. The face of each die is configured with a number of substantially parallel raised ridges and recessed valley portions oriented so as to extend diagonally across the faces of the dies. Progressing axially across the faces of the dies, it can be seen that ridges and the valleys respectively increase in height and depth relative to the clamping surfaces of the dies. The apparatus is also provided with a mechanism which causes relative movement of the dies with the workpiece clamped therebetween.
According to the method of this invention, the dies are positioned so as to opposingly face one another with their respective ridges and valleys being oppositely oriented from those of the other die. A constant diameter wire stock workpiece is positioned between the dies which cooperate to clamp the workpiece therebetween. With the workpiece clamped between the dies, the dies are axially moved relative to each other. The relative movement of the dies causes the workpiece to rotate or roll between the dies and move generally from the lead ends of the dies, over the ridges and valleys, to the trailing end of the dies where the finished masonry fastener is ejected. In moving across the face of the dies, the leading ridge of one die causes the workpiece to be deformed into the leading valley of the opposing die. After rolling across the leading ridge and valley of the dies, a helix will have been generally formed into the workpiece. The progressive increase in height and depth of the successive ridges and valley further deforms the workpiece and increases the amplitude of the helix while smoothing out the finish on the resulting fastener. After the finished masonry fastener has been ejected from between the dies, the dies return to their starting positions as another workpiece is inserted between them beginning the production of another masonry fastener.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.